Conventionally, when adjusting antenna characteristics in a non-contact type IC card/tag such as an RF-ID or NFC card/tag, a capacitor pattern and a resistance pattern for adjustment are formed on an inner side of a planar loop-shaped antenna coil formed in a spiral shape on a substrate, and adjustment of the resonance frequency of the antenna or adjustment of a Q factor is performed by cutting or etching the aforementioned patterns (for example, see Japanese Patent No. 4286977). However, since it is difficult to decrease the size of an antenna according to the technology described in the aforementioned Japanese Patent No. 4286977, a small-sized antenna has been proposed that has a shape in which an antenna coil is wound around a core formed of ferrite and/or the like (for example, see Japanese Patent No. 4883208).